High-Amylose Wheat Foods: A New Opportunity to Meet Dietary Fiber Targets for Health 1,2 3,4 5,6 3,7 3,8 1,9 5,10 M. Newberry, P. Berbezy, D. Belobrajdic, S. Chapron, P. Tabouillot, A. Regina, and A. Bird Dietary fiber is a component that is strongly associated with ABSTRACT the health benefits of plant-based foods (16,22,24,41). In par- Poor diet is recognized as a major risk factor that can be modified to ticular, dietary fiber from cereals is more effective in protecting prevent the growing prevalence of noncommunicable diseases globally against lifestyle-related, noncommunicable diseases than are and the deaths attributed to them. Enhancing the nutritional quality fibers from vegetables and fruit (24,28). It is important to note of staple foods such as cereals offers a promising strategy for address- that the evidence primarily comes from large prospective stud- ing poor diets. Whole grain wheat is of particular importance in this ies of North American and European populations in which strategy because of its well-established health-promoting potential and wheat was the predominant cereal consumed and, hence, its versatility as an ingredient, which can be used to produce foods that source of fiber in the diet (18). Indeed, wheat-based foods are appeal to consumers. With this in mind we utilized wheat breeding strategies to develop a wheat with a high amylose content (>80%) in the ubiquitous in Western diets, and although the recent trend to- starchy endosperm and have shown that this improves indices of glyce- ward consumption of gluten-free foods is lessening consump- mic and digestive health. Testing revealed the high amylose content re- tion of wheat-based foods in Western societies, this is not true sulted in significantly more resistant starch (RS) in breads and popped elsewhere, with the popularity of wheat-based foods continuing wheat (>200% more RS), udon noodles (60-fold more RS), and ramen to rise globally (20,40). Despite decades of public health cam- noodles (15-fold more RS) than was found in equivalent products made paigns promoting the benefits of consuming whole grains, how- using conventional wheats. These increases in RS were obtained using ever, many consumers still prefer and buy foods made from re- refined (white) high-amylose wheat (HAW) flour, which did not com- fined (white) wheat flour due to their greater sensory appeal promise processing, end-product quality, or sensory properties. Fur- (16,29,39). ther product development and clinical intervention trials will expand Although wheat grain composition is generally comparable the range of foods that can be made with HAW and provide a deeper understanding of the benefits HAW can provide for improving health to that of other cereals, wheat is one of the best sources of total and preventing noncommunicable diseases. dietary fiber, containing 30–100% more fiber than other eco- nomically important cereals, such as rice, maize, barley, oats, rye, sorghum, and millets (19,27). Cereal fiber diversity is lim- The health benefits of plant-based foods—fruits, vegetables, ited, however, comprising mostly insoluble fibers in the form nuts, legumes (e.g., soybeans, peanuts, pulses), and whole grain of arabinoxylans. Fructans, galactans, and b-glucans are also cereals—are well established and widely acknowledged, yet very present but at much lower levels. The resistant starch (RS) con- few people consume enough of these foods to meet the dietary tent of mainstream cereals, including wheat, is low because the recommendations established by health authorities (3,21,26). starches they contain are extensively digested in the small intes- Furthermore, government initiatives to encourage people to eat tine. Starches in popular conventional cereal-based foods are a health-promoting diet and increase their physical activity have rapidly digested in the upper gut, eliciting a sharp and pro- had limited success (13,15). New approaches that tailor the com- nounced rise in blood glucose, which is associated with an in- position of plant-based foods to the eating habits, lifestyles, and creased risk for developing metabolic and cardiovascular disor- nutritional and health requirements of contemporary consum- ders (12). Conversely, consumption of starches that are digested ers are required to provide practical approaches to address what slowly or not at all in the small intestine are associated with a is a seemingly intractable public health problem. variety of health benefits (8,25,37). Given the versatility of wheat as an ingredient, dietary promi- nence of this grain, and popularity and appeal of wheat-based 1 Commonwealth Scientific and Industrial Research Organisation, Agriculture and Food, foods, targeted changes in the nutritional content of wheat has GPO Box 1700, Canberra, ACT 2601, Australia. the potential to significantly improve the health status of indi- 2 E-mail: [email protected] viduals and broad populations. Wheat flour is an ideal vehicle 3 Limagrain Céréales Ingrédients, ZAC Les Portes de Riom, Ave George Gershwin, 63200 Riom for improving the nutritional quality of food supplies, particu- Cedex, France. larly in countries in which the quantities and types of fibers con- 4 Corresponding author. Tel: +33 (0)4 7367 1724; Fax: +33 (0)4 7367 1710; E-mail: pierre.berbezy@ sumed are less than optimal and diet-related health problems limagrain.com are prevalent. 5 Commonwealth Scientific and Industrial Research Organisation, Health and Biosecurity, Most of the fiber in grains is lost during milling to produce PO Box 10041, Adelaide, SA 5000, Australia. refined cereal flours. Nutritional manipulation of the wheat en- 6 E-mail: [email protected] dosperm provides an opportunity to greatly expand the range 7 E-mail: [email protected] of health-promoting foods that can be produced, in particular 8 E-mail: [email protected] from white wheat flour. Elevating the proportion of amylose in the endosperm results in more starch that is less digestible, a 9 E-mail: [email protected] greater RS content (32,34,36), and, accordingly, a lower available 10 E-mail: [email protected] carbohydrate density and glycemic load. RS also yields less me- https://doi.org/10.1094/ CFW-63-5-0188 tabolizable energy (23). However, for these benefits to be real- © 2018 AACC International, Inc. ized more broadly, beyond a small niche of health-conscious 188 / SEPTEMBER–OCTOBER 2018, VOL. 63, NO. 5 consumers, any changes in the physiochemical characteristics regulated. To develop waxy wheat, six alleles (two per genome) of nutritionally improved grains must not compromise the pro- needed to be downregulated. cessability or sensory appeal of the new and reformulated end Amylose, at the levels present naturally in wheat, produces products that are made from them. ~1% RS. Elevation of RS content in the grain can be achieved by increasing the proportion of amylose or amylose-like molecules Starch Molecular Structure, Digestibility, and RS using three possible mechanisms: reduced SSIIa activity, en- Starch, the dominant component of grain, provides a pleth- hanced GBSS activity, or hindered SBEII activity. The highest ora of possibilities for modification, enabling the expansion of level of amylose attained in wheat involved cosuppression of wheat grain applications with improved product functionality two isoforms of SBE (SBEIIa and SBEIIb) using a traditional and nutritional benefits. Amylose and amylopectin, the build- breeding approach. In 2006, CSIRO (Commonwealth Scientific ing blocks of starch, are made up of glucose backbones con- and Industrial Research Organisation, Australia), Limagrain nected through a-1,4 and a-1,6 linkages. The a-1,4 linkage Céréales Ingredients (France), and GRDC (Grains Research & generates linear chains, whereas branch points are created by Development Corporation, Australia) formed a joint venture a-1,6 linkages. Generally amylose is a mainly linear molecule company (Arista Cereal Technologies) to develop, patent, and that has fewer than 1% branches, unlike amylopectin, which is commercialize high-amylose wheat (HAW). Combining null highly branched (almost sixfold more branches). The spatial alleles of SBEIIa from all three wheat genomes together with location of these two polymers, their order, and the arrange- one null allele of SBEIIb from one genome resulted in a grain ment of the chains within starch granules govern the semi- with >80% amylose content (32). crystalline structure and unique functionality of a starch (9,10). The minimum level of amylose required to produce a signifi- Conventional starches are comprised of about 25% amylose; cant improvement in health outcomes is ~60% (7). Much higher the remainder is amylopectin. Amylose forms long-chain, amylose (and accordingly RS) levels are preferable to allow for double-helical crystallites, as well as single-helical inclusion greater flexibility when (re)formulating foods and to accom- complexes. The glycosidic bonds in these structures are dif- modate RS losses during food manufacture and preparation. ficult for digestive enzymes (e.g., a-amylases) to access. Con- Preliminary feeding trials in animals provided evidence that versely, amylopectin, which forms shorter chains (that also HAW contained markedly elevated levels of RS and induced form double helices) and more abundant nonreducing ends, meaningful changes in physiological and biochemical markers is more susceptible to amylolysis. In addition, linear amylose of digestive health (33). These findings are consistent with other recrystallizes during and after processing, forming double heli- studies demonstrating the benefits of RS, in particular its fermen- ces that produce retrograded starch that is resistant to enzy- tation by the saccharolytic microflora to create a healthy intra- matic hydrolysis. colonic environment, including raised butyrate levels. Subse- The amylose component of starch largely accounts for its quent preclinical studies in rats confirmed the results of earlier content of RS, which is starch that is not digested in the small work (17) and also highlighted the capacity of HAW to improve intestine and reaches the colon intact.